I understand that many people would prefer to have the "latest and greatest" but we are intentionally using the version available from the Debian repos. Yes it is a little old, but the upside is that it also will get auto security updates. It's also much less work for us to maintain.

FWIW our previous major release (v13.0) used the upstream repo (as per your suggestion) and while it worked great initially, because they don't seem to support smooth/clean upgrades (or at least they didn't) we ended up spending a ton of time supporting users to fix broken updates. That meant that auto security updates were completely out of the question but manual updates were really important (and ended up being really painful).

Are there any specific bugs or missing features in the newer upstream version? Is there some compatibility problems with newer desktop/mobile clients? Or did you just want the latest version?

If you're familiar with ownCloud, perhaps you could document the process to update to the upstream version? Then users could easily do that if they wish; or stick with the installed version if they want the auto security updates. Maybe we could even script the install (from upstream) process to make it super easy for users who want the latest?